Environmental Control for Plants using Intelligent Control Systems

Master's Thesis from the year 2005 in the subject Computer Sciences - Artificial Intelligence, grade: MSc, , course: Intelligent Control, language: English, abstract: [...] In practice, conventional controllers were used to control the system however their

parameters are empirically adjusted. Besides, the operation of these controllers relies on the

measurements provided by sensors located inside and near the greenhouse. If the

information provided by one or several of these sensors is erroneous, the controllers will not operate properly. Similarly, failure of one or several of the actuators to function

properly will impair the greenhouse operation. Therefore, an automatic diagnosis system of

failures in greenhouses is proposed. The diagnosis system is based on deviations observed

between measurements performed in the system and the predictions of a model of the

failure-free system. This comparison is done through a bank of fuzzy observers, where each

observer becomes active to a specific failure signature and inactive to the other failures.

Neural networks are used to develop a model for the failure-free greenhouse.

The main objective of this thesis is to explore and develop intelligent control schemes

for adjusting the climate inside a greenhouse. The thesis employs the conventional Pseudo-

Derivative Feedback (PDF) Controller. It develops the fuzzy PDF controller (FPDF). The

thesis also, develops two genetic algorithm (GA) based climatic control schemes, one is

genetic PDF (GPDF) and the other is genetic FPDF (GFPDF). The former uses GA to

adjust the gains of the Pseudo-Derivative Feedback Controller (GPDF) and the later uses

genetic algorithm to optimize the FPDF controller parameters (i.e., scale factors and/or

parameters of the membership functions). Finally, the thesis develops a fuzzy neural fault

detection and isolation system (FNFDIS), in which a bank of fuzzy observers are designed

to detect faults that may occur in the greenhouse end items (e.g.., sensors and actuators).

Simulation experiments are performed to test the soundness and capabilities of the

developed control schemes for controlling the greenhouse climate. The proposed schemes

are tested through two experiments, setpoint tracking test and regulatory control test. Also,

the proposed diagnostic system was tested through four experiments. Compared with the

results obtained using the conventional controllers, best results have been achieved using

the proposed control schemes.